Bilayer haptic feedback actuator

ABSTRACT

The present application relates generally to haptic feedback actuators and their construction and use in touch based systems. The haptic feedback actuators are suitably bilayer structures including at least two materials having different thermal coefficients, allowing the structure to deflect from a first position to a second position in response to heating and/or cooling of the structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/239,955, filed Aug. 18, 2016, which claims benefit of U.S.Provisional Patent Application No. 62/209,820, entitled “UltrathinBilayer Haptic Feedback Signal Generating Actuator,” filed Aug. 25,2015, the disclosures of each of which are incorporated by referenceherein in their entireties.

FIELD OF THE INVENTION

The present application relates generally to haptic feedback actuatorsand their construction and use in touch based systems. The hapticfeedback actuators are suitably bilayer structures including at leasttwo materials having different thermal coefficients, allowing thestructure to deflect from a first position to a second position inresponse to heating and/or cooling of the structure.

BACKGROUND

Haptic effects are used to enhance the interaction of an individual withan electronic device. Haptic effects enable the user to experience atouch sensation, which is typically generated by an actuator embedded inthe device. Such a haptic effect actuator provides acknowledgement orfeedback of a user's interaction with the electronic device,alternatively, or in addition to, visual and/or audio effects via adisplay or audio device. There continues to be a need for providing suchfeedback via non-visible user interfaces in a wide variety of sizes ofdevices. The size and power consumption of such haptic effect actuatorsbecome more important as an increasing number of electronic devices withuser interfaces require efficient power consumption. There remains aneed in the art for haptic effect actuators that have a low profile,such as by being thin or compact, and that consume less power.

SUMMARY

In view of the foregoing, provided herein are systems and methods forproviding haptic feedback to a user, particularly via a device having ahaptic feedback generator.

In embodiments, provided herein are systems for providing hapticfeedback to a user. The systems suitably include a device having ahaptic feedback generator, wherein the haptic feedback generatorincludes a bilayer material strip. In embodiments, in response to achange in temperature, the bilayer material strip is configured todeflect between a first position and a second position to provide hapticfeedback to the user.

Also provided herein are methods of generating haptic feedback in ahaptic feedback generator system in response to a user's contact withthe haptic feedback generator system. In embodiments, the methodsinclude increasing the temperature of a first thermal energy source/sinkin the haptic feedback generator system, thereby increasing thetemperature of a bilayer material strip in the system, and deflectingthe bilayer material strip between a first position and a secondposition to generate haptic feedback to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the present technologycan be better understood from the following description of embodimentsthereof and as illustrated in the accompanying drawings. Theaccompanying drawings, which are incorporated herein and form a part ofthe specification, further serve to illustrate the principles of thepresent technology. The components in the drawings are not necessarilyto scale.

FIGS. 1A-1B are sectional views of a system for providing hapticfeedback to a user in accordance with an embodiment hereof.

FIGS. 2A-2C are sectional views of a haptic feedback generator inaccordance with an embodiment hereof.

FIG. 3 is a graph illustrating deflection versus temperature of abimetallic strip in accordance with an embodiment hereof.

FIG. 4 is an illustration of a thermal energy source/sink comprisingfluid channels in accordance with an embodiment hereof.

FIG. 5 is an illustration of a thermal energy source/sink comprisingfluid channels in accordance with a further embodiment hereof.

FIG. 6 is an illustration of a system for providing haptic feedback to auser, comprising multiple bilayer material strips, in accordance with anembodiment hereof.

FIG. 7 is a cutaway illustration of a system for providing hapticfeedback to a user, comprising multiple bilayer material strips, inaccordance with an embodiment hereof.

FIGS. 8A-8B are sectional views of a haptic feedback generator inaccordance with an embodiment hereof.

FIG. 9 is a sectional view of a bilayer material strip in accordancewith an embodiment hereof.

DETAILED DESCRIPTION

Various embodiments will be described in detail with reference to thedrawings. Reference to various embodiments does not limit the scope ofthe claims attached hereto. Additionally, any examples set forth in thisspecification are not intended to be limiting and merely set forth someof the many possible embodiments for the appended claims.

In embodiments, provided herein are systems for providing hapticfeedback to a user. As shown illustratively in FIGS. 1A and 1B, a system100 suitably includes a device 104 having a haptic feedback generator106A, which in embodiments, is also described herein as a user touchablehaptic signal generator.

As used herein “haptic feedback” refers to information such asvibration, texture, and/or heat, etc., that are transferred, via thesense of touch, from a system as described herein to a user. Hapticfeedback can also be described as a haptic feedback signal inembodiments herein.

Examples of device 104 which can include haptic feedback generator 106Ainclude various wearables, mobile phones and tablets, touchpads,keyboards, gaming consoles and controllers, etc.

In embodiments, a user 102 interacts with device 104. In response to theinteraction, haptic feedback generator 106A deforms or deflects todeflected haptic feedback generator 106B (also described as deflectedhaptic signal generator in embodiments herein) by rising toward user 102to thereby create haptic feedback 108 (e.g., pressure, touch orvibration) from haptic feedback generator 106A. While user interactionsuitably includes touching the surface of device 104, e.g., a substrate110 of device 104 (such as a touchpad surface, touch screen, glass orplastic cover, etc.), in additional embodiments, the interaction caninclude directly touching haptic feedback generator 106A. The userinteraction can also comprise the user coming sufficiently close enoughto the haptic feedback generator to initiate the deflection withoutactually touching the haptic feedback generator.

In embodiments, haptic feedback generator 106A includes a bilayermaterial strip 202 (see FIGS. 2A-2B) for generating or providing ahaptic feedback force that may be felt by a user. The generated hapticfeedback provided by actuation of the bilayer material strip is of asufficient force so as to not be inhibited or blocked by a user's normalcontact pressure that the user may apply against a touch surface ortouchable user interface, including haptic feedback generator 106A andsubstrate 110. That is, the haptic feedback force is sufficiently strongsuch that user 102 will be able to feel the deflection of bilayermaterial strip 202 upward against the touch of the user. Methods forincreasing the haptic feedback force are described herein and includethe use of adding materials, such as further layers or additional mass,to bilayer material strip 202 to increase its thickness or overallweight.

FIGS. 2A and 2B are sectional views of exemplary haptic feedbackgenerator 106A and deflected haptic feedback generator 106B, which arehoused within or supported by device 104. As described herein, inembodiments, haptic feedback generator 106A is a touchable feedbackgenerator, though direct touching is not required to initiate the hapticfeedback as described herein.

Haptic feedback generator 106A suitably includes bilayer material strip202 coupled to a substrate 110 or device 104, for example, at opposingends 214 and 216 of the bilayer material strip 202, as shown in FIG. 2B.In embodiments, bilayer material strip 202 can be attached at opposingends 214 and 216 using, for example, various adhesives or glues, rubberattachment points, or mechanical pivots, hinges, or other connectionelements that allow the bilayer material strip to pivot or deflectbetween the first position and the second position, including allowingfor oscillation and vibration, without becoming detached from hapticfeedback generator 106A.

Upon user contact with the haptic feedback generator 106A (or substrate110), a process is initiated which causes bilayer material strip 202 todeflect from a first position (FIG. 2A), in which the bilayer materialstrip has a substantially concave profile, protruding away from theuser, to a second position (FIG. 2B), in which the bilayer materialstrip has a substantially convex profile, protruding toward the user, toprovide the haptic feedback 108 to user 102. Haptic feedback 108confirms the user contact (or sufficiently close interaction) withhaptic feedback generator 106A. As shown in FIG. 2B, the haptic feedbackgenerator 106A deflects (i.e., deforms or “snaps”) to deflected hapticfeedback generator 106B.

In embodiments, bilayer material strip 202 includes a first layer 204and a second layer 206. First layer 204 and second layer 206 aresuitably two strip-shaped (or layered) materials which are associated,bonded or otherwise adhered to one another all along a common boundary208 between first layer 204 and second layer 206. Strip-shaped denotesthat first layer 204 and second layer 206, and thus bilayer materialstrip 202, has a structure in which the length of the structure islonger than it is wide, and that has a thickness that is smaller thanits width.

In additional embodiments, bilayer material strip 202 can includemultiple layers which result in a structure displaying substantiallysimilar mechanical characteristics of bilayer material strip 202, inthat a multi-layer structure deflects from the first position to thesecond position in response to a change in temperature, as describedherein. For example, a multi-layer structure can include three, four,five, six, seven, eight, nine, ten, etc., layers, to ultimately formbilayer material strip 202. A multi-layer structure can be bound oradhered together to result in a structure similar to that of bilayermaterial strip 202, with essentially two distinct sections (each ofwhich is made up of multiple layers) of the strip that have differentmaterial properties, as described herein.

In embodiments, first layer 204 includes a first material, and secondlayer 206 includes a second material that is different from the firstmaterial. In embodiments, the first and second materials are metallicmaterials as described herein, resulting in a bimetal strip. Asdescribed herein, the first material and the second material may beselected so as to have different coefficients of thermal expansion(CTE). For example, the first material of first layer 204 in embodimentscan have a higher CTE than the second material of second layer 206. Forexample, in embodiments, the first material may be copper and the secondmaterial may be iron. Exemplary materials and structures for use inbilayer material strip 202, including bimetals, are described forexample in S. Boisseau, et al., Semi-flexible Bimetal-based ThermalEnergy Harvesters, Smart Mater. Struct. 22 (2013) 025021 (8pp), thedisclosure of which is hereby incorporated by reference herein in itsentirety.

In embodiments, first layer 204 can have a higher CTE than second layer206. Upon heating, first layer 204 expands more rapidly than secondlayer 206, causing a stress, which can be a torque or other force, to begenerated in the bilayer material 202 which subsequently causes bilayermaterial 202 to deflect from the first position to the second positionin a “snapping” motion. In embodiments, the layers which make up bilayermaterial strip 202 are bonded together and processed in a way thatestablishes a particular pre-set, shape set, or shape memoryconfiguration for bilayer material strip 202. For example, the materialscan be processed to be formed into a curved shape (i.e., the convexshape of FIG. 2A), or the materials can be processed to be formed, suchas by being stamped, into a V-shape, providing the initial or shapeset/memory configuration of the bilayer material strip, prior to thechanges in temperature that are described herein. For example, settingin the curved shape or a V-shape configuration may be accomplished viastamping (e.g., using a mechanical die or stamp to form a bilayermaterial strip into a curve or a V-shape).

By heating bilayer material strip 202, the material layers (2 or more asdescribed herein) increase in temperature. The different coefficients ofthermal expansion (CTE) of the different materials in bilayer materialstrip 202 cause differential forces between the two layers of thebilayer material strip 202 to increase. During heating, coupling momentsoccur at the fixed ends of bilayer material strip 202 (i.e., 214 and 216in FIG. 2B). The high lateral forces result from the different rates ofthermal expansion due to the differences in the coefficients of thermalexpansion of the materials which make up the strip. At a critical pointwhere the magnitude of the couples overcome the curvature in the bilayermaterial strip, causing it to snap or deform. When the strip cools, thedifferential forces or stresses in bilayer material strip 202 dissipateor relax, and contraction causes a reversing of the previous stressbuild up and returns the strip to its original shape-set curvature, orV-shape, or other configuration. See Timoshenko, S., “Analysis ofBi-Metal Thermostats,” Journal of the Optical Society of America11:233-255 (1925) (the disclosure of which is incorporated by referenceherein in its entirety) for a further description of the physicsinvolved in the movement of bilayer material strip 202 in response toheating and cooling.

The CTE difference between the materials of bilayer material strip 202enables bilayer material strip 202 to bend when heated up or cooleddown, thereby causing a mechanical movement or deflection. In oneexample, where bilayer material strip 202 is curved (as shown in FIG.2A), or V-shaped, in an initial state, bilayer material strip 202 candeform or deflect from the first position in FIG. 2A to the secondposition in FIG. 2B upon heating, and then deform or deflect back to thefirst position of FIG. 2A upon cooling.

FIG. 3 shows a hysteresis cycle for an exemplary bilayer material strip202 (suitably a bimetallic strip) for use in embodiments describedherein. FIG. 3 illustrates the deflection over a temperature range ofabout 42° C. to about 48° C., showing maximum deflection in microns.FIG. 3 demonstrates that as the temperature of the bilayer materialstrip rises (dotted line in FIG. 3), the strip reaches a “snapactivation temperature” (about 47° C. in FIG. 3), where the stripundergoes a rapid deflection without a further detectable temperaturerise. At this temperature, the bilayer material strip 202 deflects or“snaps” from a lower thermal energy source/sink, i.e., lower or bottomhot source, to be in contact with an upper thermal energy source/sink,i.e., upper or top cold source, as described below. Upon transfer ofheat from the bilayer material strip 202 to a thermal energysource/sink, which results in a cooling of the strip, the temperature ofthe bilayer material strip decreases until it reaches an inflectiontemperature of approximately 42.5° C. (see solid line in FIG. 3). Uponreaching this inflection temperature, the material deflects or snapsfrom being in contact with the upper cold source, to being again incontact with the lower hot source.

In embodiments, a displacement of bilayer material strip 202 thatresults from its deflection will be on the order of 100's of microns toseveral millimeters. This displacement or deflection is measured from aninitial position of the strip (e.g., the concave configuration of FIG.2A) to a deflected position of the strip (e.g., the convexconfiguration, toward the user, in FIG. 2B). In further embodiments, thedisplacement of the bilayer material strip caused by the deflection isabout 0.1 mm to about 5 mm, about 0.1 mm to about 2 mm, about 0.1 mm toabout 1 mm, or about 0.1-0.5 mm, so as to provide various hapticfeedback effects to a user. Such a displacement may take place only asingle time for each interaction by a user, i.e., a single deflection ordeformation for each time the user interacts with the system, or maytake place several or a plurality of times for each interaction by auser.

In other embodiments as noted above, the displacement can be on theorder of 10's of microns to 100's of microns, but occurring with afrequency of more than once per user interaction, i.e., multiple or aplurality of deflections or deformations each time the user interactswith the system, resulting in an oscillation or vibration. Inembodiments where an oscillation occurs, the frequency of oscillation ofbilayer material strip 202 can be on the order of 1 Hz to about 1000 Hz,and suitably about 1 Hz to about 100 Hz, or the order of 10-100 Hz,10-50 Hz, or about 10-20 Hz.

In order to quickly deform and return to an initial or original state orconfiguration in response to a change in temperature, including bothheating and cooling, bilayer material strip 202 is suitably of minimalthickness so as to maintain structural integrity while also allowing forhaptic feedback. The use of a thin bilayer material strip allows forrapid heating and cooling, and thus rapid deflection or snapping.Suitably, by “thin” it is meant herein that a thickness of bilayermaterial strip 202 is on the order of about 1 μm to about 1 mm, about 1μm to about 500 μm, more suitably about 1 μm to about 400 μm, about 1 μmto about 300 μm, about 10 μm to about 300 μm, about 50 μm to about 300μm, about 50 μm to about 200 μm, about 50 μm to about 150 μm, about 50μm to about 100 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm,about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about160 μm, about 170 μm, about 180 μm, about 190 μm, or about 200 μm.

It should be noted that the shape and geometry of bilayer material strip202 is not limited to only rectangular or regular-shaped elements, butcan have any geometry desired by the application or user, includingvarious disk-shapes, circular-shapes, oblong-shapes, irregular-shapes,or other suitable geometries. The dimensions (i.e., length, width,diameter, circumference, etc.) of bilayer material strip 202 can also bedependent upon the final application, but will generally be on the orderof millimeters to centimeters to 10's of centimeters.

As described herein, the process, impetus or change ofcondition/circumstance, that causes bilayer material strip 202 todeflect from the first position (FIG. 2A) to the second position (FIG.2B) to provide haptic feedback 108 to user 102 (and thus confirmingcontact or near contact) is a change in temperature or also describedherein as a thermal process. As used herein a “thermal process” refersto a process whereby heat is transferred to and/or from bilayer materialstrip 202, resulting in a change in temperature of the bilayer materialstrip and a deflection of the strip.

As shown in FIG. 2A, for example, at an equilibrium temperature (e.g.,at room temperature (about 20-25° C.) (or whatever the normal operatingtemperature of system 100 may be), bilayer material strip 202 is in aconvex configuration (i.e., curved away from user 102) and toward athermal energy source/sink 212. In embodiments, first layer 204 of thestrip has a higher CTE and is disposed above second layer 206 having alower CTE. In this configuration, bilayer material strip 202 is in afirst position (or a downward state) and bilayer material strip 202 canbe in contact with thermal energy source/sink 212. The first positionshown in FIG. 2A is suitably a shape set or shape memory curved orV-shaped configuration of the strip.

In embodiments, a change in temperature occurs as the result of atransfer of thermal energy from user 102 to a first thermal energysource/sink 212, caused by the user's contact, or sufficiently closeinteraction, with haptic feedback generator 106A or substrate 110 orother portion of device 104. In exemplary embodiments, haptic feedbackgenerator 106A can comprise two thermal energy sources/sinks 210, 212 asshown, for instance, in FIGS. 2A and 2B. Additional thermal energysources/sinks can also be utilized. Transfer of thermal energy from user102 to, for example, thermal energy source/sink 212, increases thetemperature of the thermal energy source/sink 212, which in turnincreases the temperature of bilayer material strip 202, as describedherein.

Heat transfer between user 102 and thermal energy source/sink 212 canoccur by a user's contact with thermal energy source/sink 210 (or otherportion of device 104 including substrate 110), which can then transferheat to thermal energy source/sink 212. The increase in temperature ofbilayer material strip 202 results from the direct physical interaction(including conduction via contact) between bilayer material strip 202and thermal energy source/sink 212. As described herein, the increase intemperature causes the bilayer material strip 202 to deflect from afirst position (FIG. 2A) to a second position (FIG. 2B), as a result ofthe higher CTE material (layer 204) heating more rapidly than layer 206,which results in a force effect, thermal stress, thermal bowing, ortorque in the material, and a deflection from the first position to thesecond position.

The increase in temperature can also result from heat from thermalenergy source/sink 210 transferring to bilayer material strip 202,simply by heating of surrounding air (e/g. convection) or other elementsof the haptic feedback generator 106A. In embodiments, heating ofthermal energy source/sink 210 caused by user 102 contact can transferheat to thermal energy source/sink 212 by conduction (from one thermalenergy source/sink to the other), thereby ultimately providing thermalenergy source/sink 212 with sufficient heat to increase the temperatureof bilayer material strip 202, and cause the deflection.

As used herein a “thermal energy source/sink” refers to a material thatis able to absorb and transfer heat, either as a source of heat(conducting heat to another material), or as a sink for heat (removingor dissipating heat from another material). In embodiments, the thermalenergy sources/sinks for use in the systems described herein can act asboth a source and a sink, depending on the configuration and design ofthe systems.

In embodiments, deflection of bilayer material strip 202 to its secondposition as shown in FIG. 2B causes a surface of the deflected hapticfeedback generator 106B to contact the user, or be directed toward theuser, such as shown in FIG. 1B. In embodiments, deflected hapticfeedback generator 106B may bow to protrude above or beyond the surfaceof device 100. In other embodiments, deflected haptic feedback generatorcan move substrate 110, which can be a touchpad surface, a touch screen,or a glass or plastic cover, etc., toward user 102.

In additional embodiments, the change in temperature can furthercomprise a decrease in temperature of the bilayer material strip. Thischange in temperature can occur due to a transfer of thermal energy frombilayer material strip 202 to a thermal energy source/sink (e.g., 210),as a result of removal of the user's 102 contact with the deflectedhaptic feedback generator 106B. That is, when user 102 removes thecontact from the deflected haptic feedback generator 106B, thermalenergy source/sink 210 cools via passive diffusion of heat from thermalenergy source/sink 210, allowing thermal energy from bilayer materialstrip 202 to transfer to thermal energy source/sink 210, which in turndecreases the temperature, or cools, bilayer material strip 202.

By optimizing the thickness and material selection for bilayer materialstrip 202, as described herein, this cooling can be rapid enough suchthat the temperature reduction of the bilayer material strip 202 causesthe bilayer material strip 202 to deflect from the second position (FIG.2B) back to the first position (FIG. 2A), or stated another way causesthe bilayer material strip 202 to return or relax to its shape set orshape memory first position (FIG. 2A) from the second position (FIG.2B). This process of heating, deflection, cooling, and returndeflection, can be repeated as often as desired or required by aparticular application. Such embodiments which rely on the use ofthermal energy from a user to heat (and ultimately cool) thermalsources/sinks are termed “passive” thermal processes or “passive”changes in temperature herein.

In a further embodiment, bilayer material strip 202 can transfer thermalenergy to an actively cooled thermal energy source/sink (e.g., 210),wherein the thermal energy source/sink (e.g., 210) may provide activecooling when triggered by, or in response to, the removal (or cessation)of a user's contact with the haptic feedback generator. In suchembodiments, due to the active cooling the temperature of the bilayermaterial strip 202 decreases, causing the strip to deflect from thesecond position back to the first position. As illustrated in FIGS.2A-2B, in such embodiments, bilayer material strip 202 begins in a firstposition in FIG. 2A. Following heating as a result of energy transferfrom user 102, bilayer material strip 202 deflects to a second position,as shown in FIG. 2B. When the user 102 ceases contact with the hapticfeedback generator (now deflected haptic feedback generator 106B), thistriggers the cooling of thermal energy source/sink 210, for example viavarious active methods described herein (e.g., fans, liquid channels ortubes, etc.). Thermal energy can then transfer from bilayer materialstrip 202 to thermal energy source/sink 210, resulting in a decrease inthe temperature of the strip. This thermal energy transfer causes thestrip to deflect back to the first position, as the higher CTE of theupper or first layer 204 results in a faster cooling, and allows for thereturn to the initial curved configuration of bilayer material strip 202in FIG. 2A. As described for other process herein, this process ofheating, deflection, cooling, and return deflection, can be repeated asoften as desired by a particular application.

Methods of cooling thermal energy source/sinks (e.g., 210 and if desired212), include the use of fans, water or other liquids, or other methodsof rapidly dissipating heat. In exemplary embodiments, as shown in FIGS.4 and 5 and as described herein in further detail, thermal energysources/sinks can comprise fluid channels which allow circulation offluids to aid in cooling (heat dissipation) of thermal energy sinks, andcan also be used to provide thermal energy sources (heating) in otherembodiments. The fluid channels may provide one or more passages for aliquid cooling media, or cooling liquid, to pass through, wherein theliquid cooling media is circulated through a heat exchanger thermallyisolated from the haptic feedback generator. Heat is removed from theliquid, and then the liquid is re-circulated to continue to remove heatfrom the thermal energy source/sink that is in contact with bilayerstrip 202. In another embodiment, a dual piezoelectric cooler can alsobe used to aid in cooling of the thermal energy sources/sinks. Suchpiezoelectric coolers generally rely on a bellowing action to emitpulses of air across a heat source. The action is driven by apiezoelectric actuator with the device to push air out and create aturbulent flow that entrains ambient air to create a jet-like stream andincrease heat transfer. See for example, AAVID Thermalloy's “Dual CoolJets,” low profile air movers (San Jose, Calif.).

Additional embodiments which do not rely on the use of thermal energyfrom a user contact to heat (or a user ceasing contact to cool) thermalsources/sinks are termed “active” thermal processes herein, and utilizeone or more heating elements or sources, and/or cooling mechanisms, tochange the temperature of a thermal energy source/sink and thus changethe temperature of bilayer material strip 202.

For example, an increase in temperature of the bilayer material stripcan be triggered when user 102 makes contact with haptic feedbackgenerator 106A (or substrate 100). This contact can trigger a heating ofa thermal energy source/sink (e.g., 212), which in turn increases thetemperature of bilayer material strip 202 as it is in contact withthermal energy source/sink 212. The increase in temperature causes thebilayer material strip to deflect from the first position (FIG. 2A) tothe second position (FIG. 2B) once a particular temperature/stress isreached in the strip, which results in haptic feedback to user 102. Insuch embodiments, the user's 102 contact serves simply as a signal tosystem 100 to trigger, or initiate, heating of a thermal energysource/sink (e.g., 212). Thus, it is not heat transfer from a user'stouch that is used to raise the temperature of bilayer material strip202, but simply the fact that a user is touching haptic feedbackgenerator 106A (or substrate 110 or other portion of device 100), whichthen causes the thermal energy source/sink to be heated and thusincrease in temperature. This ultimately heats bilayer material strip202, and causes the deflection from the first position (FIG. 2A) to thesecond position (FIG. 2B).

As described herein, methods for heating thermal energy source/sink 210and 212 include various conductive methods, such as the use of electricheating elements, frictional heating elements, vibrational heatingelements, and other methods of heating a thermal energy source as areknown in the art. Heating of thermal energy source/sinks 210 and 212 canoccur via any suitable method, including convention heating, conductionheating or radiation heating. Such methods can also be used to transferheat from the energy source/sinks to the bilayer material strips so asto case the changes in temperature described herein.

In embodiments, thermal energy is transferred to a second thermal energysource/sink (e.g. 210), when user 102 ceases contact with deflectedhaptic feedback generator 106B. In embodiments, as described herein,thermal energy source/sink 210 can be cooled via various methodsdescribe herein, allowing thermal energy to transfer from bilayermaterial strip 202 to thermal energy source/sink 210. This results incooling of the strip, and causes the strip to deflect back to the firstposition. As described herein, this process of heating, deflection,cooling, and return deflection, can be repeated as often as desired by aparticular application.

Both the active and passive changes in temperature and the relatedthermal processes described herein can suitably cause bilayer materialstrip 202 to oscillate in a cavity 214, such as a cavity of a device104, between a first thermal energy source/sink (e.g., 212) and a secondthermal energy source/sink (e.g., 210). As described herein, theoscillation suitably occurs with bilayer material strip 202 attached atopposing ends 214 and 216 using, for example, various adhesives orglues, rubber attachment points, or mechanical pivots, axes or otherconnection elements that allow bilayer material strip to pivot ordeflect from the first position and the second position, includingallowing for oscillation and vibration, without becoming detached fromhaptic feedback generator 106A.

The oscillation of bilayer material strip 202 creates a vibrationalhaptic feedback in a localized surface area (e.g., haptic feedback shownas 108) providing feedback to user 102 confirming contact with hapticfeedback generator 106A. As described herein, in embodiments where anoscillation occurs, the frequency of oscillation of bilayer materialstrip 202 can be on the order of 1 Hz to about 1000 Hz, and suitablyabout 1 Hz to about 100 Hz, or the order of 10-100 Hz, 10-50 Hz, orabout 10-20 Hz.

In exemplary embodiments, the thermal energy sources/sinks (e.g.,210/212) utilized to transfer heat to/from bilayer material strip 202suitably comprise a porous material. The use of a porous material allowsfor rapid heating and cooling, as desired, of the thermal energysources/sinks.

In still further embodiments, at least one material (i.e., one of firstlayer 204 or second layer 206, and suitably both) of bilayer materialstrip 202 is porous. As with thermal energy sources/sinks, making thebilayer material strip using a porous material aids in the ability torapidly heat and cool the strip, so as to allow for faster deflection insystems 100 described herein. Suitably, the porosity of the materialsreduces the thermal mass of the materials by at least about 15% belowthe thermal mass of the corresponding material having the same geometricshape, if that material was nonporous. In embodiments, the thermal massis reduced by at least about 20%, or at least about 30%, at least about40%, or at least about 50% below the thermal mass of a corresponding,nonporous material, having the same geometric shape.

In embodiments described herein, including where the change intemperature is provided by active or passive heating, systems 100 canfurther comprise a spring (including a lever, or other compressible orstretchable element) coupled to either the top surface of bottom surfaceof bilayer material strip 202. FIG. 2C shows an orientation where spring220 can be attached to bottom surface 222 of bilayer material strip 202.The spring is either mechanically elongated or mechanically compressed(FIG. 2C), during deflection of the strip, and then returns bilayermaterial strip 202 to the first position upon the user ceasing contactwith the haptic feedback generator 106A (suitably deflected usertouchable haptic feedback generator 106B), see FIG. 2A. Spring 220 is amechanical spring or lever, and is generally not activated by heating orcooling of the spring, but simply the extension or compression thatcauses the spring to return to its original shape and orientation.

In still further embodiments, user 102 may directly contact bilayermaterial strip 202, resulting in direct heat transfer from user 102 tothe strip, or from the strip to the user, heating (or cooling) the stripand causing a deflection from a first position to a second position. Asdescribed herein, depending on the coefficient of thermal expansion offirst layer 204 and second layer 206 forming bilayer material strip 202,contact between user 102 (i.e., user's finger) and for example firstlayer 204 of bilayer material strip 202 can act as a heat source or aheat sink to increase or reduce the differential stress in the bilayermaterial strip as the bilayer material strip is warmed to the skintemperature (approximately 34° C.) of the user. Exemplary materials forbilayer material strip 202 can be selected so as to have relative andabsolute coefficients of thermal expansion that operate best attemperatures around 30-40° C. Thus, contact between user 102 and bilayerstrip 202 will transfer thermal energy to cause the temperature of thebilayer material strip to rise and thereby provide haptic feedback tothe user. In such embodiments, it is not necessary to utilize separatethermal energy sources/sinks to provide the change in temperature forbilayer material strip, as all of the heating and cooling is suitablycarried out simply via heat transfer between the user and the stripmaterials.

As described herein, it is advantageous to utilize ultra-thin bilayermaterials (suitably bimetal) strips in the various systems 100.Exemplary materials include layers of Al and silica (SiO₂), or layers ofsilica and poly(vinylidene fluoride) (PVDF), which can have a totalstrip thickness in the range of dimensions suitable for bimetallicoscillators (e.g., 1-100 μm). In other instances multiple thin stripscan be arranged in parallel or stacked configuration to create bilayermaterial strip 202 having two distinct layers or sections of materialshaving different thermal and material characteristics.

In embodiments, bilayer material strip 202 includes two differentmaterial layers or sections, the materials having different coefficientsof thermal expansion, i.e., (low and high) values. One example is thecombination of two alloy metals (i.e. bimetal material); B72M (Mn Cu 18Ni 10) with a CTE=26.4×10−6/° K and INVAR® (Fe Ni) with CTE=2×10−6/° K.Additional exemplary bilayer materials, as well as bimetals include, butare not limited to, N42 (Fe Ni 42), NC4 (Fe Ni 23 Cr 3), B6M (Fe Ni 21Mn 6); Al (CTE=0.25×10−5/° K) and silicon (CTE=2.6×10−6/K); PVDF(CTE=122×10−6/K) and SiO₂ (CTE=0.4×10−6/K); PVDF (CTE=122×10−6/K) and Al(CTE=0.25×10−6/K); and PVDF and polyimide (CTE=3×10−6/K).

In additional embodiments, a single layer, or bilayer, of a metal can becombined with materials such as shape memory alloys (SMA) or shapememory polymers (SMP) to create a high-performance actuator. The shapechange resulting from the change in temperature of the metal material,combined with the actuation resulting from the actuation of a SMA or SMPcan result in synergistic effect, where the actuation is magnified oramplified. Such materials can be prepared in multiple layered structuresand utilized in the various embodiments and applications discussedherein.

Processing and manufacturing of bilayer material strip 202 as describedherein includes for example, processing the strip materials to be usedto make the bilayer strip, such as a bimetal alloy, by a rolling or aplating process to bond the two metal layers together. In the case whenusing aluminum (Al) and silicon, thermal evaporation (sputtering method)(PVD) can be used to fabricate the material. For instance, thin film Alcan be sputtered onto a thin section of a Silicon material. A thin oxidelayer (such as Al₂O₃ or SiO₂) can be formed between the Al and siliconmaterial layers to provide electrical protection (for the purpose ofthis description, such a structure would still be considered to be abilayer material in accordance with the description herein). Forexample, when using PVDF and Al, first a thin film of PVDF material canbe deposited using film casting methods (spin coating, solventevaporation). In a next step, a thin layer of Al can be deposited ontoone side of PVDF material strip. When using other material combinationssuch as PVDF/polyimide, a simple bonding mechanism or plasma enhancedadhesion methods can be employed to enhance the adhesion between the twomaterials. Moreover, a thin metal material layer can be laminatedbetween two polymer layers in order to be used later as a (resistive)heating element (source).

The methods and systems described herein are designed to operate underconditions in which heat transfer occurs very quickly, resulting in avery fast system response time (strip snapping). The very thin dimensionof the bilayer material strips 202 translates to a very low thermalmass, so that strip heating and cooling can occur very quickly. The rateof cooling is limited by the rate of thermal conduction (heat transferthrough conductive heat transfer) of the bilayer material strip 202.Thermal energy is suitably removed from the surface of the bilayermaterial strip 202, and thus utilizing a thin bilayer material strip 202minimizes the amount of thermal energy that can be retained, aiding inrapid heating/cooling and rapid deflection.

As described herein, whether using a passive or an active temperaturechange of the bilayer material strip, cooling elements such as thoseshown in FIGS. 4 and 5 can be implemented. FIG. 4 shows a micro channelheat exchanger 400 where micro channels 402 in a top section 404 of athermal energy source/sink receive coolant and guide the coolant fluidto the micro channels 402 of the lower section 406 as the space betweenthe top and bottom section has heat transfer fins 408 in a corrugatedpattern extending between them as is well known in radiator technologiesto provide a large surface area to which the air flowing sideways (seearrow) through the fins can be exposed. As described herein, use of sucha cooling mechanism provides for rapid thermal transfer from bilayermaterial layer 202 to thermal energy source/sink (e.g., 210), to allowfor quick deflection and return deflection of bilayer material layer202. A similar micro channel system can also be used to heat a thermalenergy source/sink, when required, as described herein, for examplethrough the use of a heated liquid. FIG. 5 shows a similar embodiment ofa microchannel heat exchanger 510, where only a single set of microchannels 402 are utilized.

In addition to micro channels through thermal energy sources/sinks,fluid in channels 802 can also be passed above or below thermal energysources/sinks (e.g., 210/212) to control temperature (see FIG. 8A). Inother embodiments, fluid can be passed above or below bilayer materialstrip 202 in flexible tubes or channels 804, without the need foradditional elements acting as thermal energy sources/sinks (e.g.,210/212) (see FIG. 8B). While flexible tubes or channels 804 are shownextending only over and above a partial section of bilayer materialstrip 202, it should be understood that tubes or channels 804 suitablycan extend over the entire length of the bilayer material strip 202.

In still further embodiments, cooling or heating elements, such aselectronic heating elements, or fluid channels, can be added directly tobilayer material strip 202, including for example by passing fluidchannels or tubes 806 through a porous material of the first and secondlayers 204, 206, to utilize the strips not only as deflecting elements,but also as self-heating and self-cooling elements. See FIG. 9. Singleor multiple channels or tubes 806 can be used as required to properlycontrol the temperature of bilayer material strip 202. In embodiments,tubes 806 can be made from flexible materials to allow for thedeflection and movement that occurs with bilayer material strip 202.

In other embodiments, system 100 can comprise a dual piezoelectriccooler to act as a low power active cooling air mover (see cooler 902 ofFIG. 9). In another instance, a set of opposed plates can be charged toprovide ionic charging of air molecules which when they move, influencethe air molecules adjacent to the ionized molecule to move as well toinduce air motion for enhanced cooling (see set of plates 904 of FIG.9).

The transition temperature and temperature difference for bilayermaterials is suitably as low as possible. For example, bilayer materialstrip 202 is configured to deflect or “snap” at a temperature betweenabout 30° C. and 47° C. Bilayer materials are suitably selected andconfigured (programmed) to work under a variety of desired temperaturesand temperature differences.

The ultrathin systems as described herein can be implemented on manydevices (wearable, mobile, gaming, mobile phones, touchpads etc.) toprovide haptic feedback and require minimal energy (from user's bodyheat or external heating devices).

The time lapse between application of a user's finger to substrate 110or haptic feedback generator 106A of system 100 and the user detectinghaptic feedback in response is called the response time of the system.The response time of the system is dependent on the materials chosen tomake up the bilayer material strip, and the physical configuration asdescribed herein. In addition, the response time of a particular systemis dependent on the thermal mass and rate of heat transfer between thehot and cold thermal sources/sinks and the materials of the bilayermaterial strip. Suitably, the response time of the systems describedherein are on the order milliseconds (i.e., 1-100 milliseconds).

In embodiments, the following parameters are taken into consideration toimprove the response time (performance) of the systems:

-   -   use of porous materials (e.g., porous Si, PVDF, AL, etc.) to        minimize the thermal mass of each layer of the bilayer material        strip to achieve better performance (an improved response time);    -   use of very thin (micron size) but strong materials;    -   use of thin cooling devices such as dual piezoelectric coolers        to maximize cooling;    -   modification of bilayer material strip 202 from two to three or        more layers to improve conductive heat transfer within and        between material layers;    -   configuring of bilayer material strip 202 in a sealed (or closed        cooled) system that may include use of a thermal transfer fluid        in contact with an outer or inner cooling passage surface of the        respective components to improve the rate of heat transfer        between system components having different temperatures as the        actuation process is initiated and progresses.

The haptic feedback process can also be accelerated by configuring thebilayer material strip 202 between two thermal energy source/sinks,i.e., heating sources (or thermal heat sinks) to accelerate the heatingof the bilayer material strip. For instance, the top surface of thebilayer material strip can be exposed to a thermal mass having atemperature T1 (cold source) and the bottom surface of the bilayer stripcan be configured to thermally connect with a second thermal mass havinga temperature T2 (hot source) (see FIGS. 2A and 2B). The higher CTEmaterial in the bilayer material strip being on top, facing the coldsource inside the actuator system where the bimetal strip moves.

When using such a system configuration, the initial activation time andthe subsequent rate at which the haptic feedback generator vibrates ordeforms depends on the rate of thermal energy transfer from the thermalenergy sources/sinks (hot and cold) to the bilayer material strip 202and associated temperature fall and rise of both layers in the bilayermaterial strip, the CTEs (coefficients of thermal expansion) of the twomaterials making up the bilayer strip, and their ambient temperaturegeometry (configuration), as set during system assembly.

FIGS. 6 and 7 show an alternate arrangement of a haptic feedbackgenerator as described herein. With reference to FIG. 6, a plurality ofbilayer material strips 202 are shown assembled in a parallelconfiguration in a cavity 702 (see FIG. 7) of the haptic feedbackgenerator, and are also shown disposed between two thermal energysources/sinks (210/212), e.g., a hot source on first sides of theplurality of strips and a cold source on second sides of the pluralityof strips.

FIG. 7 shows a cutaway view where thermal energy sources/sinks 210/212of the haptic feedback generator have been removed and bilayer materialstrips 202 are pictured. FIG. 2 provides a sectional view of anexemplary bilayer material strip 202 of the plurality of bilayermaterial strips shown in the embodiment of FIGS. 6 and 7. The bilayermaterial strips as shown are ultrathin strips (straight or having somecurvature) made, as described herein, of two different materials withtwo different coefficients of thermal expansion. They are arranged in aparallel configuration. Any number of bilayer material strips can beused, suitably 2 or more, more suitably about 2 to about 100 bilayermaterial strips, or about 10 to about 100, about 20 to about 100, about20 to about 50, or about 10, about 20, about 30, about 40, about 50,about 60, about 70, about 80, about 90 or about 100 bilayer materialstrips. The bilayer material strips may have similar or varyingthicknesses, suitably in the range of about 10 μm to 100 μm.

Also provided herein are methods of generating haptic feedback in ahaptic feedback generator system in response to a user's contact withthe haptic feedback generator system. In embodiments, such methodscomprise increasing the temperature of a first thermal energysource/sink in the haptic feedback generator system, thereby increasingthe temperature of a bilayer material strip in the system. The methodsfurther comprise deflecting the bilayer material strip between a firstposition and a second position to generate haptic feedback to the user.

As described herein, in embodiments, increasing the temperature of thefirst thermal energy source/sink involves transferring thermal energyfrom the user to the first thermal energy source/sink as a result of theuser's contact with the haptic feedback generator system (i.e., apassive temperature change as described herein). In further embodiments,increasing the temperature of the first thermal energy source/sinkutilizes heating the first thermal energy source/sink, triggered by theuser's contact with the haptic feedback generator (i.e., an activetemperature change as described herein).

In further embodiments, the methods further include transferring thermalenergy from the bilayer material strip to a second energy source/sink,when the user ceases contact with the haptic feedback generator, anddeflecting the bilayer material strip from the second position to thefirst position. In still further embodiments, thermal energy istransferred from the bilayer material strip to a second thermal energysource/sink, when the user ceases contact with the haptic feedbackgenerator, and deflecting the bilayer material strip from the secondposition to the first position.

While various embodiments have been described above, it should beunderstood that they have been presented only as illustrations andexamples of the present technology, and not by way of limitation. Itwill be apparent to persons skilled in the relevant art that variouschanges in form and detail can be made therein without departing fromthe spirit and scope of the present technology. Thus, the breadth andscope of the present technology should not be limited by any of theabove-described embodiments, but should be defined only in accordancewith the appended claims and their equivalents. It will also beunderstood that each feature of each embodiment discussed herein, and ofeach reference cited herein, can be used in combination with thefeatures of any other embodiment. All patents and publications discussedherein are incorporated by reference herein in their entirety.

What is claimed is:
 1. A system for providing haptic feedback to a user,the system comprising: a device having a haptic feedback generator,wherein the haptic feedback generator includes: a bilayer material stripcomprising at least a first material and a second material that havedifferent coefficients of thermal expansion; a first thermal energysource/sink; and a second thermal energy source/sink, wherein inresponse to a change in temperature, the bilayer material strip isconfigured to deflect between a first position and a second position toprovide haptic feedback to the user, wherein the change in temperatureis an increase in temperature of the bilayer material strip that occursdue to a transfer of thermal energy from the first thermal energysource/sink to the bilayer material strip, the transfer triggered whenthe user makes contact with the haptic feedback generator, wherein theincrease in temperature causes the bilayer material strip to deflectfrom the first position to the second position, and wherein the thermalenergy is transferred from the bilayer material strip to the secondthermal energy source/sink in the second position, to allow the bilayermaterial strip to switch from the second position back to the firstposition.
 2. The system for providing haptic feedback of claim 1,wherein the bilayer material strip further includes a shape memory alloyor a shape memory polymer.
 3. The system for providing haptic feedbackof claim 1, wherein the bilayer material strip is a bimetallic strip. 4.The system for providing haptic feedback of claim 3, wherein thebimetallic strip has one of a curve profile and a V-shaped profile. 5.The system for providing haptic feedback of claim 1, wherein the bilayermaterial strip has a thickness on the order of about 1 μm to about 200μm.
 6. The system for providing haptic feedback of claim 1, wherein thethermal energy is transferred from the bilayer material strip to thesecond thermal energy source/sink when the user ceases contact with thehaptic feedback generator.
 7. The system for providing haptic feedbackof claim 1, wherein the bilayer material strip deflects from the firstposition to the second position in a direction toward the user.
 8. Thesystem for providing haptic feedback of claim 1, wherein the hapticfeedback is a vibrational haptic feedback effect created by oscillationof the bilayer material strip.
 9. The system for providing hapticfeedback of claim 1, wherein the first thermal energy source/sinkcomprises a porous material.
 10. The system for providing hapticfeedback of claim 1, wherein the first thermal energy source/sinkcomprises fluid channels, electrical heating elements, frictionalheating elements, or vibrational heating elements.
 11. The system forproviding haptic feedback of claim 1, wherein the second thermal energysource/sink comprises fluid channels.
 12. The system for providinghaptic feedback of claim 1, wherein a bottom surface of the bilayermaterial strip is coupled to a spring that returns the bilayer materialstrip to the first position upon removal of the user's contact with thehaptic feedback generator.
 13. The system for providing haptic feedbackof claim 1, wherein at least one material of the bilayer material isporous.
 14. A method of generating haptic feedback in a haptic feedbackgenerator system in response to a user's contact with the hapticfeedback generator system comprising: increasing the temperature of afirst thermal energy source/sink in the haptic feedback generatorsystem, triggered by the user's contact with the haptic feedbackgenerator, thereby increasing the temperature of a bilayer materialstrip in the system; deflecting the bilayer material strip between afirst position and a second position to generate haptic feedback to theuser; transferring thermal energy from the bilayer material strip to asecond thermal energy source/sink in the second position; and deflectingthe bilayer material strip from the second position back to the firstposition.
 15. The method of claim 14, wherein the transferring thermalenergy from the bilayer material strip to the second energy source/sinkoccurs when the user ceases contact with the haptic feedback generator.16. The method of claim 14, wherein the bilayer material strip furtherincludes a shape memory alloy (SMA) or a shape memory polymer (SMP)actuator, and the deflecting the bilayer material strip between thefirst position and the second position to generate haptic feedback tothe user further includes actuating the SMA or SMP actuator.
 17. Themethod of claim 14, wherein the deflecting from the first position tothe second position is in a direction toward the user.
 18. The method ofclaim 14, wherein the haptic feedback is a vibrational haptic feedbackeffect created by oscillation of the bilayer material strip.
 19. Themethod of claim 14, wherein the increasing the temperature of the firstthermal energy source/sink occurs via fluid channels, electrical heatingelements, frictional heating elements, or vibrational heating elements.20. The method of claim 14, wherein the second thermal energysource/sink comprises fluid channels.